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What are the risk factors?

Many factors can increase your risk of breast cancer, but they do not mean that you will definitely develop it. You can also have none of the known risk factors and still get breast cancer. If you are worried, speak to your doctor.

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  • Being female is the biggest risk factor – 99% of breast cancer cases are diagnosed in women.
  • Risk increases with age for both men and women.
  • About three quarters of breast cancer cases are in women over the age of 50. Free breast screening is available.
  • Dense breast tissue (as seen on a mammogram) increases your risk.
  • Breast implants or breast augmentation does not increase your risk of breast cancer.
  • Being overweight or gaining weight after menopause. Losing weight to a healthy range can lower this.
  • Drinking alcohol – the more that you drink, the higher your risk. If you choose to drink, the alcohol guidelines suggest you drink no more than 10 standard drinks a week, and no more than 4 standard drinks on any one day.
  • Not getting enough exercise or not being physically active.
  • Smoking tobacco may increase your risk.
  • About 5–10% of breast cancers are due to an inherited breast cancer gene such as BRCA1 or BRCA2.
  • Most people with breast cancer do not have a strong family history. However, having several close relatives (e.g. mother, sister, aunt) on the same side of the family who have had breast or ovarian cancer may increase your risk.
  • Several close relatives on the same side of the family with prostate or pancreatic cancer may increase your risk.
  • Using menopause hormone therapy (MHT) containing both oestrogen and progesterone, for long periods of time and over many years.
  • Taking the pill (oral contraceptive) for a long time (small increase).
  • Using some hormonal IUDs for a long time (small increase).
  • You or your mother using diethylstilboestrol (DES) during pregnancy.
  • Transgender women taking gender-affirming hormones for more than 5 years.
  • Having been previously diagnosed with breast cancer, LCIS or DCIS.
  • Some non-cancerous conditions of excessive growth of breast cells (hyperplasia).
  • Having radiation therapy to the chest area for Hodgkin lymphoma.
  • Males with a rare genetic syndrome called Klinefelter syndrome. Those with this syndrome have three sex chromosomes (XXY) instead of the usual two (XY).
  • Never having given birth may increase risk.
  • Starting your first period (menstruating) before the age of 12 may increase your risk.
  • Being older than age 30 when you gave birth to your first child increases your risk.
  • Not having ever breastfed may increase your risk.
  • Going through menopause after the age of 55 may increase your risk.

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This information is reviewed by

This information was last reviewed July 2022 by the following expert content reviewers: A/Prof Elisabeth Elder, Specialist Breast Surgeon, Westmead Breast Cancer Institute and The University of Sydney, NSW; Collette Butler, Clinical Nurse Consultant and McGrath Breast Care Nurse, Cancer Support Centre, Launceston, TAS; Tania Cercone, Consumer; Kate Cox, 13 11 20 Consultant, Cancer Council SA; Dr Marcus Dreosti, Radiation Oncologist and Medical Director, GenesisCare, SA; Dr Susan Fraser, Breast Physician, Cairns Hospital and Marlin Coast Surgery Cairns, QLD; Dr Hilda High, Genetic Oncologist, Sydney Cancer Genetics, NSW; Prof David W Kissane AC, Chair of Palliative Medicine Research, The University of Notre Dame Australia, and St Vincent’s Hospital Sydney, NSW; Prof Sherene Loi, Medical Oncologist, Peter MacCallum Cancer Centre, VIC; Dr W Kevin Patterson, Medical Oncologist, Adelaide Oncology and Haematology, SA; Angela Thomas, Consumer; Iwa Yeung, Physiotherapist, Princess Alexandra Hospital, QLD.